A new surface wiping test to study surface disinfection by a novel chemical combination

Effective biofilm disinfection is difficult to be implemented in healthcare settings and industry. In particular, surface disinfection is crucial to prevent microbial contaminations. However, disinfectants misuse has led to an increased concern on the existence of resistance and cross-resistance phenomena due to inadequate disinfection practices. The purpose of this study was the development of a formulation to be used for surface disinfection with wipes. The idea was to produce a formulation based on the combination between the quaternary ammonium compound - cetyltrimethylammonium bromide (CTAB) and a natural product - cinnamaldehyde. In addition, a new disc methodology to assess wiping efficiency was developed based on the Wiperator test (E2967-15) and on the quantitative test method for the evaluation of bactericidal and yeasticidal activity on non-porous surfaces with mechanical action employing wipes in the medical area, 4- field test (EN 16615:2015). The combination of CTAB and cinnamaldehyde was synergic in terms of antimicrobial action against Escherichia coli and Staphylococcus aureus. After stablishing the final formulation, wiping efficacy was assessed with the new methodology. In this case, a contaminated surface (6.20 ± 0.21 log₁₀ CFU of E. coli and 7.10 ± 0.06 log₁₀ CFU of S. aureus) was wiped using two different wipes in terms of composition, thickness and porosity (A and B). After wiping the contaminated surface with wipe A, without the formulation, 3.42 ± 0.46 log₁₀ CFU (E. coli) and 5.38 ± 0.20 log₁₀ CFU (S. aureus) remained on the surface while in the presence of the formulation the bacteria present were under the limit of detection for E. coli and 2.76 ± 0.22 log₁₀ CFU for S. aureus. The formulation was also able to prevent the transfer of bacteria to clean surfaces after wiping the contaminated surface. In the case of wipe A, after wiping the contaminated surface and the subsequent 2 clean surfaces, a total reduction of 4.35 ± 0.22 log₁₀ CFU and 4.27 ± 0.22 log₁₀ CFU was achieved when the wipe was impregnated with the formulation in comparison with 2.45 ± 0.41 log₁₀ CFU and 1.50 ± 0.35 log₁₀ CFU of removal just by mechanical action for E. coli and S. aureus, respectively. For wipe B a general lower reduction was observed but the same behaviour was detected with the use of the formulation when comparison to just mechanical action. This work highlights the enormous potential of combinatorial approach to increase the efficacy of already used biocides diminishing their in-use concentration and consequently their environmental and public health burden.

 

Acknowledgements

This work was financed by: UIDB/00511/2020 of the Laboratory for Process Engineering, Environment, Biotechnology and Energy – LEPABE - funded by national funds through the FCT/MCTES (PIDDAC); POCI-01-0145-FEDER-030219, POCI-01-0247-FEDER-035234; POCI-01-0145-FEDER-028397; POCI-01-0247-FEDER-033298; POCI-01-0145-FEDER-006939, funded by FEDER through COMPETE2020 – Programa Operacional Competitividade e Internacionalização (POCI) and by national funds (PIDDAC) through FCT/MCTES. Grant attributed by Portuguese Foundation for Science and Technology (FCT) to Joana Malheiro (SFRH/BD/103843/2014) and Manuel Simões (SFRH/BSAB/150379/2019).